The present invention relates to a playback device for disc-shaped record carriers with signals stored in the grooves of the record and, more particularly, to an arrangement for moving the disc playback head during playback in a direction transverse to the direction of the grooves.
In connection with the method for recording signals according to the high density storage technique which has become known as the "picture record technique" and playback by pressure scanning, U.S. Pat. No. 3,767,848, issued Oct. 23, 1973 to E. Schuller et al, describes a playback device which includes a pickup for the picture signals which moves radially across the record during playback and is guided by a positive guide means which is coordinated with the rotation of the record. The playback device includes an elastic mount for the pickup and the advancing of the pickup can be switched off, or the advancing device is connected with the turntable drive shaft of the turntable via an infinitely or stepwise variable drive assembly, so that it is possible to effect slow motion or elapsed time display of the recorded signal. The pickup mount is so designed that when the radial advance is switched off the pickup is carried along over a few grooves of the record due to the groove guidance before it jumps back as a result of the elasticity of the mount.
The drawback of such an arrangement is the fact that the jumping of the pickup is dependent on a series of contingencies over which the operator has no influence and which prevent jumping of the pickup at precisely predetermined points over defined distances. These contingencies, are, inter alia, the manufacturing variations in the pickup and its mount as well as the unavoidable tolerances which occur during manufacture of the record carrier. Although experiments have been made to favor jumping of the pickup at predetermined points in the groove by deforming the groove, the results were unsatisfactory since this still did not permit a precise predetermination of the changeover of the pickup into an adjacent groove.